The in vivo mechanism for the clotting of blood requires conversion of the soluble protein fibrinogen into the insoluble protein fibrim in a reaction catalyzed by the enzyme thrombin. Thrombin is the activated form of prothrombin, a globulin circulating in the plasma. The conversion of prothrombin to thrombin requires a number of reactions involving the interaction of blood fractions having thermoplastic activity, including Stewart-Prower factor, Factor V, Factor VII and calcium. Several additional substances having thromboplastic activity have been identified, and are generally referred to by the genus thromboplastin.
Under the influence of thrombin, which is actually a proteolytic enzyme, and other blood factors, the blood protein fibrinogen loses several polypeptide chains to form fibrin. The fibrin then undergoes a polymerization to produce fibrin polymers which contribute to the physical properties of the clot.
The thrombin catalyzed polymerization of fibrinogen into fibrin is reproducible in vitro. For example, a system composed of purified fibrinogen, thrombin and added calcium produces the so-called Fibrin S polymer by spontaneous reversible polymerization. Polymerization is said to be reversible, due to the solubility of the Fibrin S polymer in dilute (0.03%) HCl.
However, an acid insoluble polymer of Fibrin I (insoluble fibrin) can be formed in vitro for example by addition of small amounts of serum to the in vitro system.
The serum contains a factor responsible for inhibition of the reversible polymerization of fibrin. This stabilizing factor in serum which enters the clotting sequence after fibrin has been formed, known as the Laki-Lorand factor (LLF) or fibrin stabilizing factor (FSF), is known to exhibit a useful stabilizing effect on the vitro polymerization of fibrinogen. Under the nomenclature proposed by the International Committee for the Standardization of the Nomenclature of Blood Clotting Factors, LLF is designated Factor XIII.
Thus, it is known that purified thrombin and fibrinogen, together with a variety of known adjuvants, can be combined in vitro to produce a polymer having great potential benefit, both as a hemostatic agent and as a tissue adhesive. Because of the rapid polymerization upon intimate interaction of fibrinogen and thrombin, it is important to maintain these two blood proteins separate until the application site. Previously, these materials have been delivered by devices such as a dual syringe apparatus which makes it possible to deliver the fluids for mixture at a small point.
One apparatus for applying a fibrinogen-based tissue adhesive is disclosed in U.S. Pat. No. 4,359,049 to Redl, et al. Redl discloses a complicated mechanism in which two standardized one-way syringes are held in a support having a common actuating means guided along a rod. Each of the delivery ends of the syringes is inserted into a collection manifold for delivery of the two components for mixing and delivery optimally through a mixing needle. However, it is often desirable or necessary to cover a broad area of a wound, either to stop bleeding, to fix tissue or to prevent infection.
Notwithstanding the contribution of Redl, there remains a need for a fibrinogen dispensing kit which is inexpensive, suitable for entry into the sterile field, and adaptable for convenient recharging of the fibrinogen or thrombin from a single source, as may be required during prolonged surgery or other procedure. In addition, the dispensing kit is advantageously capable of delivering the two blood proteins either at a focused point of delivery or as an aerosol mist for covering a region of tissue.